Synergistic effect of surface active agent in defect passivation by for ambient air-synthesized halide perovskite solar cells

The unavoidable defect states located on the surface or grain boundaries (GBs) of the perovskite film can seriously deteriorate the performance and stability of perovskite solar cells (PSCs). In this work, an efficient and lowcost surface-active agent, sodium laurylsulfonate (SLS) has been incorporated into perovskite precursors in order to achieve effective defect passivation of humid air-fabricated PSCs. The zwitterionic SLS agent can not only improve crystallinity of perovskite film but also play the role of defect passivation originated from both negative and positive-charged defect states. Density Functional Theory (DFT) calculation proves that the sulfonic acid group S=O and Na(+ )cations in SLS passivator can bond with the uncoordinated lead and halogen ions, leading to the suppression of carrier non-radiative recombination. As a result, the performance of champion device with SLS additives improves from 16.68 to 19.93%. Moreover, SLS passivation agent can also enhance the long-term stability of unencapsulated devices under ambient condition, which maintains 91% of its initial efficiency after 21 days. This study probes into the zwitterionic surface active agent with pi-conjugated system for long term defect passivation of perovskite optoelectronic devices.